Hello,
First post here. I've aquired a small Honda portable generator (vintage 1977). The model is EG 1500 (1.5kw output). This generator is equipped with an automatic voltage regulator (avr) that is physically damaged. This particular avr uses the input of 120vac from the stator and apparently rectifies it for use as an output to the brushes to control rotor field current and therefore voltage output. Frequency appears to be regulated by engine rpm and does not appear to be controlled by the avr. The avr assembly is filled with what I believe to be fiberglass resin (or similar) material to seal all the components. This stuff is very difficult to remove and I don't think I can do it without destroying all the internal components. Honda no longer services this regulator and the universal ones are quite expensive. I'd like to recreate a suitable circuit to regulate the generator as a project for my own learning. At a minimum, I would need to rectify 120vac and use the the corresponding dc to drive the rotor field current to maintain 120vac under varying loads. Rotor resistance is 54 ohms. There is also an external cap of 200uF 250WV attached to the original avr. There are 4 wires from the stator for input to the avr (althought I'm not sure all would be required) and the coresponding 2 dc output wires from the avr to the rotor brushes. Any suggestions would be appreciated.

Ohh Boy.. you want to build a 1.5Kw voltage regulator? Components will be quite expensive. Did you try for spares from any one of the new 1.5Kw models? Maybe that might work. And it would be a lot cheaper for you. check about it before you jump in.

hi,
I'm doing a similar project.. i have to design an AVR for a single phase alternator(220v, <10 KVA).The existing AVRs have a feature of underfrequency shut down... i.e. below a specified frequency, which can be adjusted by a potentiometer...
Kindly suggest me a frequecy to voltage converter IC which is low in cost..

Ohh Boy.. you want to build a 1.5Kw voltage regulator? Components will be quite expensive. Did you try for spares from any one of the new 1.5Kw models? Maybe that might work. And it would be a lot cheaper for you. check about it before you jump in.

Click to expand...

So typically what is in these AVR's that is so expensive that they charge between 200 and 400 dollars for them?

I have 4 Coleman Powermate 5000 watt gens in my shop for repair. There is about 5 or 6 film caps about 10 resistors 2 transistors, some doides of different types, a divice I am told is a switch rated at 400v 10 amp it looks like a scr or voltage regulator (T-220 case) and 2 or 3 electrolitic capacitors.

Just a bunch of junk on a circuit board. Powermate went out of business and my customers are left with a useless machine after only 1 or 2 uses.

I suspose I could draw up the board and try to ID the components but it must be a simple circuit there isnt much to this PCB. Could anyone help trouble shoot it? All 4 have over heated the "switch" device. Or if there is some other way to skin this cat.

I will do my best to make a diagram of the board and its components. It may possibly work for different gens. It has exciter ac 2 yellow wires that feed a pair of diodes with a common output which after feeding a filtering capacitor end up on one of the leads of the "switch" and a center tap that feeds one of the brushes to the rotating fields. The middle lead on the Switch" feeds the other brush. It has 2 other wires that feed the output voltage from the main stator to the control circuit. I will also post the "switch" info, the guy at the electronics supplier had trouble finding it on his listings. From what I see there are 2 circuits on the board one is for making dc for the rotating fields and the other is to turn the "switch" on and off in relation to the main stator output. I suspect the control circuit has a problem and thats why the "switch" looks fried.
Stew

This is exactly whats going on with the Honda that I originally posted about. Unfortunately, the resin they used to seal all the components prevents me from seeing any of the components for schematic purposes. Like you, I agree that this component does not seem overly complex and that was the reason for my initial post. The generator I have is also set up the same way with a exciter winding that is rectified and then used for the controlling dc rotor current. It also has two wires from the main stator winding for voltage monitoring. So, 4 wires in (2 from exciter winding, 2 from main stator), 2 wires out (dc for rotor current). My suspicion is that the dcv output for rotor current control would be in the range of 12-85v with max 3A current. Unlike a previous post suggesting this is a big deal, like you I don't believe this is nearly as expensive as some here seem to believe. I also concur that the price of these things is rediculous and for those of us with either discontinued parts or bankrupt manufacturers, we have no choice. I hope you can see enough of your regulator to generate a schematic. Thanks for your post.

It turns out I should be able to get a good pic or print of my PCB. Turns out 3 of what I thought were small caps are maybe varisitors. I got all the junk off the board. I think I will unsolder everything and put it in the scanner. Hopefully someone here will be able to improve it or suggest what might be wrong with the circuits. I just found out today that the local Canadian Tire has a bunch of these gens and would like a solution too. Maybe I will get a chance over the weekend. I will take some pics too.
Stew

re: can't get attachments to work
File format is important. Images are preferred in .png format, as they are not "lossy" like .jpg format. There is a size limit of 100k for .png files.
If the files are too large, they won't upload.
.ZIP format files can also be attached; I think they're limited to 1 megabyte.

re: can't get attachments to work
File format is important. Images are preferred in .png format, as they are not "lossy" like .jpg format. There is a size limit of 100k for .png files.
If the files are too large, they won't upload.
.ZIP format files can also be attached; I think they're limited to 1 megabyte.

Click to expand...

Let me know how my jpg pics look to you before I put up a few more
Stew

No there was a heat sink it didn’t have any heat conducting paste on it. It might have dissipated heat better if it was up in the air. But this board is screwed to the inside of the endbell of the generator so there is lots of air flow. I am posting a copy of the PCB with the copper traces marked over the component print. If something doesn’t look right I will have another look. Getting down to my questions if there is enough info. Does this board have a problem or is the transistor just too small? Is there a good site to check how to test some of this stuff ? I have basic skills but no electronics training as such. I am a motor winder/machinist, I have an Industrial Electrical Ticket so I have a understanding of some of it. Is there a good online place to lay out circuits and test them? Something like Electronic Work Bench or a free down load of something like that but simple ?
Stew
In my pic the conections are marked from the gen. 2 blacks are hooked to the main winding output either 120v or 240v the 2 yellow and the blue are the exciter supply with the blue the center tap or common. I will try to check tomorrow on voltages and currents from the gen at normal operating output by using external excitation.

Attached Files:

To the best of my ability I drew out the PCB If something doesn't make sense point it out and I will have a look at the board. The transistors C E B may not be marked in the proper order but they are the same as on the PCB. I did it that way to minimize the lines that had to be crossed over in my drawing. Didnt get time to test anything yet. As soon as I do I will post if and what was bad or damaged.

Also I tried to delete the pic of the PCB I traced over in marker. I need to repost it with a few repairs. I made a few traces that dont exist.

Attached Files:

Attached is an LTspice schematic of the sketch you did which is more readable for understanding the circuit function.

Click to expand...

Well it must have taken about an hour to draw it up, but I wasn't very pleased with it. Surprizing where things are actually connected once you trace the PCB out.

I will get some numbers to you later today. I wondered if thats what might be going on with it. There is lots of heat as the board is turning brown. Where did you get the schematic? LTspice? Is that a program?

Well I only got so far on testing and checking output on this generator.
Rotating field resistance 28 ohms Read through the brushes.
The following readings were taken from the 120 v output
No excitation 2.2 v
At 20 vdc external excitation 99.7 v
Fed through 2 diodes and a var. resistor using the generators excitation winding 120 vac with 30-31 vdc reading on the brushes. at 1.1 amps
Maxed out with no resistance 142 vac at 82 vdc at the brushes.

Then I got ready to test with a load and bang the connecting rod broke and smashed a hole the size of my fist in the engine case. This machine was destined to die no matter what. It had only 50 hours tops of use for 2 power outages. About 1 1/2 years old.